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# What causes Frame Dragging (gravity friction)?

Wed 26 Mar, 2008 09:27 pm
Frame Dragging is a phenomena predicted by GR and confirmed by experiment.

Rotational Frame Dragging occurs when a massive object (like a planet, or neutron star) rotates and 'drags' on the space-time around it almost as though there were friction between the mass and the space around it. However, the force causing this is NOT friction.

The thought experiment used to describe Frame Dragging is to imagine a paper plate with a puddle of Honey on it. Then you place a superball in the middle of the honey and rotate the superball. If there are peppercorns sprinkled in the honey, you will see the peppercorns which are nearest the superball pulled along by the viscosity of the honey. A similar effect occurs in the gravitational field of a rotating body.

The following quote is in the article linked above:
Quote:
The rotation of the Earth does twist the spacetime frame like the ball twists the honey, although it is not caused by "friction" between the Earth and local spacetime. It is unclear to scientists exactly how this phenomena occurs. The theory of general relativity suggests that spacetime and masses have a mysterious mutual "grip" on each other.

I would like to hear some reasonable (no magic please) speculation and discussion as to how this effect can occur. How can there be 'friction' in gravity?
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rosborne979

1
Thu 27 Mar, 2008 05:55 am
Does the Frame Dragging cause the rotating mass to slow down at all?

I'm having a hard time imagining this effect without thinking of it like friction, in which the effect on one object has a counter effect on the other (and a transfer of energy). But in the case of Frame Dragging I'm not sure there is any transfer of energy between the various components of the system.
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g day

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Sat 12 Apr, 2008 08:45 pm
Because relativity states space tells matter how to move and matter tells space how to warp!

You have a large mass at least spinning - if not in movement - you will be affecting the curvature of spacetime around you. If this object is a Sun - then its radiating tremendous energy and losing mass every second - so the gravity well isn't constant over the longer term - energy is escaping into space - changing the topology of said local space.

Another factor to consider is are the two or more bodies in orbit of solid / rigid matter or do these bodies have either viscous surfaces or inner volumes of greatly varying density? Consider the Earth / Moon system - Earth has oceans that the Moon (and Sun) effect. Gravitational interaction affects the land too - just about 1/30th as small as the oceans. Rising tides exerts forces that water friction resists to quell over time each day. Such interaction between the Earth and Moon slows both the rotational period of each, and slows both down in motion relative to each other To counterbalance this the Earth and Moon recede from each other about 3cm each year! Two water planets orbiting each other would recess over time faster than two ice planets of equal mass!

Friction is a bad term to use and a steady state model will over-simplify things. May I suggest de-mystify this by restating the problem. Describe the forces of change acting on a system over time - concentrate on envisioning the changing topology (curvature due to energy density) of the region considered as time advances and energy density (what energy is where changes) changes - topology (the curvature of the spacetime field) changes.

The key is to stop thinking of gravity as a force of attraction and see it as a curvature of a 3 dimensional field, then ask are things generating or affecting this field changing over time? By the time our Sun ends its life - it will have radiated so much mass that to maintain equilibrium the Earth / Sun equilibrium our planets orbit will shift to beyond where Mars lies today (another 50 million kilometres further out)! Imagine the Sun went nova and blew itself into eight parts that flew away at say 80 percent of light speed - hence leaving our solar system within a day - the planets would drift apart because the spacetime around them has un-curved - not because any force within the space time intself has pushed them away!
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rosborne979

1
Sun 13 Apr, 2008 11:29 am
Thanks G_Day. I'll have to think about this. I'm not sure I understand yet.
akaMechsmith

1
Fri 21 Nov, 2008 07:35 pm
@rosborne979,
The "frame drag" as an effect of motion has also puzzled me. But if one can figure it out (which I think possible) then gravity simply becomes a field generated by relative motion and "curved space" becomes simply the result of motion through spacetime. I think that you can chase this effect all the way into atomic theory and through intergalactic space but I certainly don't know it!

For instance, an orbit is a straight line in curved spacetime. OR an orbit is a curved line in straight spacetime. If the frame drag effect turns out to be a force or field similar in some respects to an electromagnetic field then we don't have to curve space anymore. It could prove interesting. I am only speculating at this point and certainly couldn't argue it!

Just for grins look at a magnetic drive in an aquarium filter. The parts are linked only by magnetic fields.

Then change fields and do it with a universe or an atom. Best of luck,

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dpfitz

1
Wed 14 Jul, 2010 08:18 am
Magnetism can be seen as electrons frame dragging other electrons with their spins.

Can gravity be quarks frame dragging other quarks with their spins?

Stephen Wolfram's book, "A New Kind of Science" gives us three (3) very important facts:

1. Mathematics can only explain simple things.

2. You need a model to explain complicated things.

3. But - a simple model can explain complicated things.

It looks to me like we have a PHASE model here.

"in phase attract"

Type those three words - above - into Google (Include quote marks) to learn not only the basics of electricity but how all the fundamental forces work.

Or click the following link that will give you the same page in Google. http://www.google.com/search?hl=en&source=hp&q=%22in+phase+attract%22&btnG=Google+Search

Not only do all electric motors obey these phase laws but this entire universe seems to as well.

(Click link below.)
Edit [Moderator]: Link removed

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HexHammer

1
Sat 4 Sep, 2010 12:45 pm
@rosborne979,
I belive gravity to be much like magnetism in many ways, but quite different in it's projection as gravity in my theory has liniar projected lines, where magnetism has donut shaped lines.
As magnetism can "grip" things, so can gravity, but the real question is, is it pushing or dragging?
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mike rooke

2
Tue 27 Dec, 2011 01:46 pm
@rosborne979,
'Friction' and 'drag' are inevitably metaphorical, and are meaningful only in the context of a mechanistic modelling of this alleged effect. The model is dualist in the sense of basing itself on the discreet separation of matter from space-time. Mass and metric are but phenomenal aspects of a more fundamental unity - that which we may tentatively refer to as an energy distribution/density. The first stept to conceptualising this would be to postulate its manifestation in a matter-spacetime continuum. The tensor analysis of General Relativity is suggestive of a route to overcoming the dualism, but in the last analysis remains a prisoner of it. 'Gravity friction' is only a valid hypothesis as the expression of a particular mechanistic model. The alternative starting point suggested above may be a more fruitful approach.
rosborne979

1
Tue 27 Dec, 2011 08:31 pm
@mike rooke,
Thanks Mike. What you said "sounded" pretty good. It had lots of nice words in it like "tensor" and such. But I'm not sure it made any sense.
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ProfChuck

1
Tue 8 Jan, 2013 07:25 pm
@mike rooke,
I don't know if this thread is still active but if it is I have a question about frame dragging. If the rotating mass is completely homogeneous the relativistic frame dragging (Lense-Thirring effect) should fit general relativity. So is it possible to separate the effect produced by rotating homogeneous bodies from those that have quadrupole or higher moments?
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